1. Field of the Invention
The invention concerns a metal halide vapor lamp, particularly for application in aquaria, with a fill containing GdBr3, HoJ3, DyJ3, CsJ and TlJ.
2. Background Art
A metal halide vapor lamp of this kind is on the market place under the mark SLI Aqua Arc which contains 27.8% of weight GdBr3, 22.2% of weight HoJ3, 29.6% of weight DyJ3, 13.0% of weight CsJ and 7.4% of weight TlJ. This known metal halide vapor lamp has a CCT (Correlated Color Temperature) of 9300 K (i.e. a color correlation temperature equal to the temperature of 9300 K of a black body), a color point having the coordinates X=0.277 and Y=0.312, an efficiency of 60 lm/W and a CRI (Color Rendering Index) of 80.
Notwithstanding that with this lamp the luminous efficiency can be called particularly well, the color temperature could be higher and also the color rendering could be a bit better. The said coordinates X and Y lie in the green region of the CIE chromaticity diagram, whereby the colors of the objects illuminated, particularly of an aquarium, appear not that natural.
Besides from U.S. Pat. No. 4,992,700, a Three-Lines-Lamp (red-green-blue) is known having a fill from Indium, Zink, Lithium and Thallium which finds application in reprographic purposes and in the field of projection.
U.S. Pat. No. 5,965,984 describes a metal halide lamp for use as a light source for a LCD-Projector or the like which has a light transmitting container with a fill which consists of a starting gas which is an inert gas, of a least one halide of indium and of a halide of a rare earth metal, the latter being selected from the group consisting of Terbium, Dysprosium, Holmium, Erbium, Thulium and from mixtures from the same group.
Further, a high pressure discharge lamp can be taken from DE 101 01 508 A1 which can be used particularly in headlamps of power driven vehicles and which contains a fill from mercury, an inert gas and a metal halide mixture from at least one halide, whereby at least one part Indiumjodide or Thalliumjodide is contained in the metal halide mixture, which should influence the color point of the light radiation generated and should increase the quantity of light, for example, so the blue or yellow portion in the spectrum of the discharge could be increased.
Finally the DE 200 04 732 U1 teaches a low pressure gas discharge lamp for illumination of aquaria having a fill from a rare gas or a rare gas mixture and mercury, in which the UV-radiation of the mercury discharge is transformed by a specific fluorescent into the desired blue radiation. A disadvantage of this lamp consists in the low radiation density which is sufficient to illuminate an aquarium in its upper region only.
The object underlying the invention is seen in providing a metal halide vapor lamp of the kind mentioned initially of which the color temperature on the one hand and the color rendering index on the other hand are higher and which particularly makes the colors of the objects irradiated appearing especially natural.